Environmental causes of human congenital malformations: The physician's role in dealing with these complex clinical problems caused by environmental and genetic factors

When I had completed medical school and graduate school, the scientific world did not even have the correct figure for the number of human chromosomes. Greggl had recently described the teratogenicity of rubella virus infection during pregnancy The teratogenic risk of the folic acid antagonists was established2" and there were experimental studies indicating that nutritional deficiencies could produce birth defects in anirnal~.~ What have we learned and accomplished in the past 50 years? Thousands of previously unknow7n genetic diseases have been described and many of their genes have been identified since the 1 9 5 0 ~ . ~ ~ The fields of prenatal intrauterine diagnoses, intervention and treatment have been created. Metabolic and biochemical screening have become standard care for pregnant women and newborns. Over 50 teratogenic environmental drugs, chemicals and physical agents have been described7-lo using modern epidemiological tools and the talents of clinical dysmorpho1ogists."-l7 The basic science and clinical rules for evaluating teratogenic risks have been established (Table l ) . I s The development of the rubella vaccine and the recognition of the importance of adequate folic acid intake in women of reproductive age are forerunners for the prevention of birth defects from teratogenic infectious agents and nutritional components that are important for normal development. The completion of the first stage of the Human Genome Project in the year 2000 offers the geneticist and teratologist immense opportunities to evaluate the concepts of polygenic and multifactorial e t io log ie~ '~ ,~~ of congenital malformations.